After the War the old 5 meter band (56 - 60) was changed to 50 - 54 mcs. The FM assignment was 52.5 and up. FM deviation was 15 kcs. 52.500 + .015 = 52.515, add a 10 kcs guard band and you get a round number 52.525. It wasn't very crowded back then. Paul w0rw